The Cochlear Prosthesis Human Psychophysics Project concerns the psychophysical attributes of implant stimulation and their impact on the design of signal processors for enhancing the intelligibility of auditory signals. A fundamental limitation faced by cochlear implant technology is the limited capacity to transmit psychologically relevant information about the acoustic signal. Improved auditory prostheses depend on better ways to relate device characteristics to device performance for optimizing a given device to the patient, and on breakthroughs in signal encoding and neural stimulation which increase information throughout. Multiple-channel electrode design has been proposed as a means for improving information capacity of the prosthesis, yet it appears that cross-talk among channels limits such improvement in practice. We will test the hypothesis that measures of channel interaction which reflect masking of envelope fluctuations in suprathreshold signals are better predictors of device performance than measures of masked detection threshold. Once implanted, improvements in device performance can be achieved only through modifications in the signal processor. We will evaluate the hypothesis that waveshape is a salient feature of implant stimulation which, furthermore, can be used to increase the information capacity of encoding algorithms. Finally, we will develop acoustic models of several properties of implant stimulation as a method for measuring experimentally optimal performance for specific encoding schemes.